Foreground Render washes out background Photo
I used the Node Editor and added the Emission shader between the Image Texture and the Material Output. I set the Emission shader to 0.85 this seemed to give the right balance of light to offset the lighting that I was using and mostly restored the colours in the background image.

I'll add some more lighting to match the image lighting better, adjust the Field of view, camera distance etc to get the focus looking right and match the image blur.

Many thanks for the advice.